my MAF car has a map too?

[President_Douche]

we were talking about it in this thread Voltage cap for MAP 2.2L

but i figured someone might see this and know whats going on...

My car is a MAF car but has a map sensor fender mounted as well...

anyone else have this going on as well or know what is up?

i noticed it at first when my car the a map CEL....

any and all help appreciated

[President_Douche]

any ideas?

[my4isflat]

The ECU uses that MAP sensor to determine the atomospheric pressure outside the engine.

[President_Douche]

wouldnt the atmospheric sensor do that? this has the atmo sensor and a map sensor

[VIN CODE 6]

A Pressure Sources Switching soleinoid (PSSS) is used on 1995 and newer Subaru vehicles equipped with OBD II. The PSSS functions via an ECM ground signal and switches to allow atmospheric pressure to reach the pressure sensor during engine start, then every 30 minutes or 3.1 miles. The PSSS switches to allow maniflod pressure to reach the pressure sensor when not switched to atmosphere.

The red one is the pressure sources switching solenoid. The one with the hose attached is a pressure sensor. Basically the system compares manifold pressure to atmospheric to make sure they are the same or very close because it's N/A otherwise the ECU sees this as a fault.

The pressure sensor functions to monitor manifold and atmospheric pressure. PSSS position determines the pressure
source. Changes in pressure (positive or negative) produce a changing reference voltage signal. Reference voltage signal changes are used by the ECM to determine optimum ignition timing and injection duration.

Maybe someone can help me with a theory though. My thought is if you tee into the line going to the pressure sensor from the intake so the pressure sensor sees only manifold pressure all the time, will it work? In theory the sensor doesn't care what source the pressure is from only the value. There has to be some range to the sensor because consider this....say you live at elevation, 10,000 ft. or so and you drive to a location at sea level, effectively the system would see this as boost because atmospheric pressure is rising as you get lower in elevation. The system just makes sure the 2 sources match but if it's only from 1 source the value will be consistent and therefore "match" and keep the ECU happy.

I feel this could be a way to use the stock ECU on a mildly boosted (5-6 psi) application because as stated above the ECU corrects fuel and ignition timing according to the pressure value. The average pressure increase from 10,000 ft to sea level is .934 in/hg per 1000 ft or around 9 psi total. Hmmm!
Anyone know if this works or not. I know alot of people put check valves in line with the sensor to prevent CEL's but you have to look at how the system works. If it's comparing boosted manifold pressure to atmospheric of course it will throw a CEL but if it sees the same value all the time and it's within parameters why would it care whether or not the car has forced induction? Anyone care to comment on this, I'm waiting on my turbo kit so I can try this for myself.

[joejoe69]

here's your fix...

BOOST NANNY